Concentration of acrosome stabilizing factor (ASF) in rabbit epididymal fluid and species specificity of anti-ASF antibodies

Variation among individual bulls in the distribution of acrosomal tyrosine-phosphorylated proteins in epididymal and ejaculated spermatozoa

In Japanese black cattle, AI severely subfertile males have occasionally been found. In order to solve this problem, we previously asserted the need for exact examinations of acrosomal tyrosine-phosphorylated proteins and acrosome morphology in cryopreserved spermatozoa. In the present study, we further investigated acrosomal tyrosine-phosphorylated proteins in spermatozoa before cryopreservation and examined possible relationships between these phosphoproteins and acrosome stability. Ejaculated, epididymal and cryopreserved spermatozoa were subjected to examinations of general characteristics (motility, shape and acrosome morphology) and indirect immunofluorescence of acrosomal phosphoproteins. Unlike all general characteristic parameters, the distribution of acrosomal tyrosine-phosphorylated proteins in ejaculated and cauda epididymal spermatozoa varied considerably among bulls and was linked to the maintenance of morphologically normal acrosomes in cryopreserved spermatozoa or ejaculated spermatozoa after 270 min incubation. Moreover, the distribution of these phosphoproteins was arranged in the spermatozoa of the proximal epididymides. These findings indicate that acrosomal tyrosine-phosphorylated proteins are distributionally arranged during early process of sperm maturation, that their distribution of cauda epididymal and ejaculated spermatozoa are largely different among bulls, and that varied states of acrosomal phosphoproteins may result in individual differences in acrosome stability among bulls.

Secretion patterns and effect of prostate-derived granules on the sperm acrosome reaction of rabbit buck

There is increasing evidence that the particulate fraction of seminal plasma plays an important role in reproduction of several mammalian species. However, the origin and role of these granules in the physiology of rabbit spermatozoa is partially unknown. The aim of this study was to investigate the implication of prostate gland in the production and secretion of granules into the rabbit semen and the role of prostate-derived granules in the sperm acrosome reaction. Light and electron microscopy of the prostate gland showed that the anterior and middle tracts of the prostate (namely the proprostate and prostate, respectively) are chiefly implicated in the secretion of granules of different size: smaller granules (SG; 0.5 μm) and large granules (LG; 4 μm). Two major patterns of secretion were identified, based on electron microscope views: storage granules (large granules) seem to empty inner smaller granules directly into the duct by exocytosis, or the storage vesicle itself is released in toto into the ducts (diacytosis). In vitro experiments using granules from vasectomized rabbits, to exclude testicular origin of granules, showed that granules reduce the acrosome reaction of Percoll-selected spermatozoa, independently of the size. Interestingly, spermatozoa incubated with heat-treated granules showed a higher sperm acrosome reaction rate, suggesting a potential role of granule-derived proteins in this process. Inhibition of the acrosome reaction is a crucial event in rabbit reproduction; ejaculated spermatozoa have to wait for a long time (8-16 h) for egg availability in the female tract after mating. Taking together, our results demonstrate that prostate granules secreted either by exocytosis or diacytosis can preserve spermatozoa fertilizing ability, by preventing sperm acrosome reaction. The type of granule-derived proteins or other macromolecules implicated in this process should be further investigated.

Secretory proteins from the epididymis and their clinical relevance

The literature pertaining to epididymal proteins and their functions in fertilization is reviewed. Animal studies have indicated that specific epididymal proteins may be involved in aspects of sperm motility, sperm-zona binding and the acrosome reaction. If analogous proteins in the human exist, use could be made of them in the andrology clinic. Currently, only one specific epididymal protein (alpha-glucosidase) is routinely measured for semen analysis. Glucosidase secretion, in addition to reflecting inflammation of the organ, is used in conjunction with other markers of human fertility to identify patients with ductal occlusion for whom bypass operations may be useful therapy. Glucosidase inhibitors have been used to improve the assay, by establishing true semen blank values, and to quantify histochemical activity in frozen tissue sections. From its localization in the human corpus and cauda epididymidis, neutral glucosidase can not be used to identify occlusion in the proximal regions of the duct. Other proteins may be valuable markers of these regions. In the future, other specific proteins of epididymal origin found in seminal fluid could well illuminate dysfunction of the organ in cases of infertility or be end-points of the disruptive action of drugs aimed at the epididymis.

Enigmas of mammalian gamete form and function

The gametes of man and some other Eutheria have been manipulated successfully for practical reasons, but many gaps remain in our basic understanding of the way that they function. This situation stems not least from a failure to recognize the extent to which eutherian spermatozoa and eggs, and elements related to their operation, have come to differ from those of other groups. Novel features in the male that reflect this include a radical design of the sperm head with the acrosome seeming to function primarily in egg-coat binding rather than its lysis, a multifaceted post-testicular sperm maturation and an androgen/low-temperature-regulated system of sperm storage--both tied to the epididymis, a variable male accessory sex gland complex, and descent of the testis and epididymis to a scrotum. In the female, such novelties are represented in a need for sperm capacitation, in an unusual regulation of sperm transport within the oviduct, in the cumulus oophorus and character of the zona pellucida around the small egg, and in a unique configuration of gamete fusion. The collective evidence now suggests that many of these features reflect a new fertilisation strategy or its consequences, with most being causally linked. One initial 'domino' in this regard appears to be the small yolkless state of the egg and its intolerance for polyspermy, as determinants of the unusual mode of oviductal sperm transport and possibly the existence and form of the cumulus oophorus. However, a particularly influential first 'domino' appears to be the physical character of the eutherian zona pellucida. This differs from the egg coats of other animal groups by virtue of a resilient elasticity and thickness. These qualities allow this primary and often only coat to stretch and so persist during later expansion of the blastocyst, usually until close to implantation. At the same time, the dimensions, physical character, and particularly the relative protease-insensitivity of the zona appear to have had profound effects on sperm form and function and, more indirectly, on sperm-related events in the male and the female tract. Marsupials display some similarities and also some strikingly different features, against which the enigmas of the eutherian situation can be evaluated.

The Identification of Mouse Sperm-Surface-Associated Proteins and Characterization of Their Ability to Act as Decapacitation Factors1

Mammalian spermatozoa must undergo capacitation before acquiring the ability to fertilize the oocyte. This process is believed to be initiated following the release of surface-associated decapacitation factors that are elaborated by both the epididymis and the male accessory organs. Herein, we report the identification of a number of proteins that are actively released from the surface of mouse spermatozoa during capacitation in vitro. As anticipated, the addition of these factors back to suspensions of mouse spermatozoa was shown to suppress several correlates of the capacitation process. Specifically, they induced a significant, dose-dependent inhibition of the ability of spermatozoa to undergo a progesterone-induced acrosome reaction and to bind to the zona pellucida in vitro. Inhibition of these functions was associated with the suppression of tyrosine phosphorylation in the sperm plasma membrane but had no effect on the phosphorylation of internal proteins in either the sperm head or tail. This inhibitory activity was attributed to a subset of the isolated proteins compromising at least four putative decapacitation factors. These proteins were identified via tandem-mass spectrometry amino acid sequence analysis as plasma membrane fatty acid binding protein, cysteine-rich secretory protein 1 (CRISP1), phosphatidylethanolamine binding protein 1 (PBP), and an unnamed protein product that we have termed decapacitation factor 10 (DF10). Of these proteins, PBP was identified as a primary candidate for a decapacitation factor.

Rabbit epididymal secretory proteins. II. Immunolocalization and sperm association of REP38

Polyclonal antibody was used to partially characterize REP38, a major rabbit epididymal secretory protein. Western blot analyses and immunohistochemistry indicated that REP38 is only expressed in regions 5 and 6 of the epididymis (corpus epididy-midis) and is localized in the supranuclear region and microvilli of the principal cells in these regions. It was not expressed in other tissues of the body. In region 8 (cauda epididymidis), REP38 was detected in the luminal border and cytoplasm of scattered principal cells, indicating that it may be reabsorbed in this region. This protein accumulated on the sperm plasma membrane downstream of region 5 and was localized predominantly over the acrosomal and postacrosomal regions of the head and the middle piece. Although tightly bound to epididymal sperm, REP38 migrated to the equatorial segment under conditions in vivo that would promote capacitation. When tested in vitro, anti-REP38 IgG reduced the percentage of ova fertilized in a concentration-dependent manner, apparently by blocking sperm-egg fusion.

Fertility reduced by immunization with p84: A human sperm-coating antigen in the mouse

Background : p84 is an 84-kDa protein with the ABO (H) antigenic epitope, and it is also a member of the family of sperm-coating antigens. In order to investigate whether the antibodies against p84 reduce fertility in mice, p84 and lactotransferrin (Lf), whose N-terminal sequence is similar to that of p84, were injected into female mice. Results : When p84 was used as the immunogen, the fertilization ratio was 37.5% lower than that of female mice immunized with no antigen (control group; P < 0.01). When Lf was used as the immunogen, there was no significant difference in the fertilization ratio between the Lf and control groups. Sera from female mice immunized with these antigens showed no agglutination against human erythrocytes, suggesting that the ABO(H) determinant site on p84 is not the factor reducing fertility. Although the titer of antibody (IgG) against p84 in serum from female mice immunized with p84 was generally higher than that against Lf, the titer was not related to the reduction of fertility. Conclusion : We conclude that an injection of p84 can reduce the fertility of female mice by inducing antibodies against p84. Our results suggest that the antibodies may act to inhibit the sperm-egg interaction, and that the binding site is the carbohydrate chain of p84, excluding the ABO (H) antigenic epitope, rather than the p84 protein itself. (Reprod Med Biol 2002; 1: 35-39).

Posttranslational processing of PH-20 during epididymal sperm maturation in the horse

It is generally accepted that spermatozoa become functionally mature during epididymal transit. The objective of this study was to determine whether the cellular location of equine PH-20 is modified during epididymal transit and, if so, the mechanism for such modification. Sperm were isolated from caput and cauda epididymal regions from stallions undergoing castration (n = 7) and used as whole sperm cell or subjected to nitrogen cavitation for isolation of plasma membrane proteins. Both caput and cauda sperm and sperm protein extracts were subjected to N-deglycosylation, O-deglycosylation, or trypsinization. The SDS-PAGE and Western blot analysis using a polyclonal anti-equine PH-20 IgG were performed in sperm extracts, and indirect immunofluorescence on whole sperm was also performed to determine the cellular distribution of plasma membrane PH-20 following similar treatments (deglycosylation or trypsinization). Hyaluronan substrate gel electrophoresis was performed to detect hyaluronidase activity in SDS-PAGE proteins. Western blots revealed significant differences in electrophoretic migration of PH-20 proteins from caput and cauda epididymal sperm. No effect was seen from deglycosylation treatments on the Western blot pattern; caput protein extracts exposed to trypsin showed the same band pattern as extracts from the cauda epididymis. N-deglycosylation resulted in the loss of hyaluronidase activity of sperm from both epididymal regions, whereas O-deglycosylation or trypsinization did not affect hyaluronidase activity. In caput epididymal sperm, the PH-20 protein is distributed over the entire sperm head; in cauda epididymal sperm, it is restricted to the postacrosomal region. No effect from deglycosylation on the cellular distribution of PH-20 was observed; however, treatment with trypsin changed the cellular distribution of PH-20 in caput sperm similar to that of the distribution of cauda sperm. These results suggest that PH-20 distribution during epididymal maturation is dependent on proteolytic trypsin-like mechanisms and, possibly, on complementary membrane-associated factors.

Biochemical characterization of sialoprotein "anti-agglutinin" purified from boar epididymal and seminal plasma

Sialoprotein "anti-agglutinin," previously shown to inhibit sperm head-to-head agglutination, is found in both boar epididymal and seminal plasma. The present report characterizes anti-agglutinin by mass spectrometry, by N-terminal amino acid sequence analysis, and by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) and Western blotting techniques to assess phosphate content of the molecule. Anti-agglutinin had the SDS-PAGE mobility of approximately 25 kDa. By electrospray ionization-mass spectrometry, however, mass spectra of anti-agglutinin were characterized by two major peaks (19,379-19,382 Da and 19,395-19,397 Da) and several minor peaks. Mass spectrometry of tryptic peptide fragments of deglycosylated anti-agglutinin and amino acid sequence analysis revealed that the protein has a unique peptide-mass fingerprinting of fragments (12,668 Da, 5,209 Da, 1,226 Da, and 1,168 Da) and a novel N-terminal amino acid sequence (KTDDY AISGA KEEEF YDYME ELYAV), respectively. Additionally Western blot techniques, using commercially available monoclonal antibodies, were used to detect presence of phosphothreonine and phosphoserine substituents, but two different monoclonal antibodies did not detect phosphotyrosine. Moreover, treatment with two different alkaline phosphotases converted the molecule, as assessed by SDS-PAGE and detection by silver stain, from the parent form of about 25 kDa to forms of approximately 19 kDa (similar to that assigned by mass spectrometry) and/or 15 kDa. Original antiserum generated toward, and reacting with native anti-agglutinin, reacted only with 19 kDa form. These results are consistent with the conclusion that the native anti-agglutinin may be a novel protein that is phosphorylated at serine and/or threonine residues.

Identification of anti-agglutinin for spermatozoa in epididymal boar plasma

The present report identifies epididymal boar anti-agglutinin and examines its effect on sperm motility. Boar spermatozoa from the cauda epididymidis were washed and incubated in modified Krebs-Ringer bicarbonate at 37 degrees C (5% CO2 in air). In the samples washed three or five times and then incubated for 3-5 h, higher rates (72-79%) of spermatozoa were associated with one another at the acrosomal region, mainly in groups of 2-5 cells (head-to-head agglutination), and many cells exhibited intensively flagellant and/or circular types of movement but rarely progressive motility. The addition of epididymal plasma or 25 kDa protein purified from it markedly inhibited the occurrence of head-to-head agglutination in washed spermatozoa, whereas heat treatment and subsequent removal of insoluble materials reduced the anti-agglutination activity of epididymal plasma. The percentages of progressively motile cells in the samples incubated with epididymal plasma or 25 kDa epididymal protein rose coincident with the reduction of sperm agglutination. These findings demonstrate that the 25 kDa epididymal protein is an anti-agglutinin for the cauda spermatozoa and that it effectively functions to maintain progressive motility of the cells in vitro.